Jaw engaging mechanism



y 1959 Y H. 'IYROYEGER 2,885,895 I JAW ENGAGING MECHANISM Filed'Oct. 24, 1955 FIG. 1

FIG. 2

INVENTOR.

HE NR) TROEGER United States Patent JAW ENGAGING IVIECHANISM Henry Troeger, Ramsey, N.J., assignor to Bendix Aviation Corporation, Teterboro, N.J., a corporation of Delaware Application October 24', 1955, Serial No. 542,147

7 Claims. (Cl. 74-7) This invention relates to starter jaw engaging mechanism. It is particularly concerned with providing new and useful improvements in controlling jaw advancement and retraction in engine starter mechanism.

An object of the invention is to prevent undue axial pressure of the starter and engine jaws against one another at the time of engagement.

Another object of the invention is to insure full engagement of starter and engine jaws despite close tolerance differences in the position of the jaw members.

A further object of the invention is to prevent ratcheting of the jaw teeth during engaging and disengaging operations.

A still further object of the invention is to provide means for insuring the retracted position of the starter jaw subsequent to its disengagement.

A feature of the invention is certain spring controlled means whereby the engine jaw is caused to yield slightly during engagement operations, whereby a smooth engagement of the jaw members is obtained despite close tolerance differences in the positioning of the jaw members.

Another feature of the invention is certain flyweight mechanism for promoting a frictional force against a. rotating spline nut, whereby the starter jaw is caused to advance axially into engagement with the engine jaw.

A further feature of the invention is other centrifugally operating mechanism whereby the starter jaw is retained in retracted position after disengagement, and is restrained against moving back into engagement with the engine jaws, whereby conventional ratcheting of the jaw members is avoided.

The invention further lies in the particular construction of its component parts, as well as in their general organization and cooperative association to effect the purposes intended.

The foregoing and other objects and advantages of this invention will appear more fully hereinafterfrom a consideration of the detailed description which follows, taken together with the accompanying drawings wherein an embodiment of the invention is illustrated. It is to be expressly understood, however, that the drawings are for purposes of illustration and description and are not to be construed as defining the limits of the invention.

In the drawings:

Fig. 1 is a longitudinal sectional view of a com-bustion turbine engine starter embodying the invention;

Fig. 2 is a detail directed to the flyweight mechanism; and

Fig. 3 is a section on the line 3--3 of Fig. 2.

In describing the invention in further detail, reference is directed to the drawings wherein there is shown in' a turbine driven engine starter, a combustion chamber 1. Hot gases of combustion exit from the latter through nozzles 2 to drive a turbine member 3 carrying a drive shaft 4 which is rotatably supported in suitable bearings 5, 6. A pinion gear 7 formed on shaft 4 drives a ring gear 8 through idle gears 9. The latter rotate on bearingslo ice mounted on pins 11. Pins 11 are carried by a bell member 12 having an elongated axial shaft extention 14 in the interior of which is retained the bearing 6. In this hearing 6 the left end of the turbine shaft is rotatably supported. Ring gear 8 is formed in the right end of member 12.

A hub portion 15 of extension 14 carries a sun gear 16 which, through planetary gearing 17, rotatable in a surrounding fixed ring gear 18, and through trunions 19 supporting the planetary gears 17, drives a disc clutch barrel member 20.

The barrel member rotates a spline nut 21 through a disc pack clutch 22. One half of the interleaved discs of this pack are carried by the internal wall of the barrel member, and the other half of which are carried in the external surface of the spline nut. Nut 21 surrounds a starter jaw member 23; and internal helical splines of the nut engage complementary external splines of the jaw member. Upon rotation of the spline nut, the starter jaw is caused to travel axially leftward to bring a ring of teeth 24 formed in its end wall into engagement with a ring of complementary teeth 25 formed in the end face of a flange piece 26 of an associated engine jaw member 27.

The engine jaw member has an axially projecting hollow stub shaft 28 which is slidably engageable, by straight splines 29 thereon, in the engine shaft, not shown, of an associated engine.

The engine jaw, here, is associated with the starter assembly as a part thereof, and is resiliently held thereto. To this end, the extension 14 of the bell member provides in its left end an axial pocket in which is received the headed end 30 of an axially disposed shaft 31. A confined coil spring 13 surrounds the shaft and tensions the headed end 30 into abutment with the rear wall of the pocket. A retaining sleeve nut 32, threaded onto the end of extension 14, has a reduced overhanging end piece which fronts the open end of the pocket and retains the spring in the latter. An open ended cup member 33, axially mounted at one end to the inner face of the engine jaw, projects into the hollow interior of the starter jaw in slightly spaced relation to the inner wall surface of the latter and sleeves the retaining nut 32. The shaft 31 projects freely through the cup member into the hollow interior of the stub shaft of the engine jaw, wherein an enlarged cylindrical end 34 of the shaft is contained in the inner race of a ball bearing 35. The outer race of the latter is retained in the surrounding wall of the stub shaft. Flange and nut means carried by the enlarged end of the shaft at opposite ends of the bearing prevents axial escape of the shaft from the latter. The cup member 33 serves in aligning the teeth of the starter jaw with those of the engine jaw. The shaft and spring means serve to axially position the engine jaw so that its teeth will be in close spaced relation to those of the starter jaw.

Rotation of the spline nut 21 rotates the starter jaw with it. A friction force applied by arcuate flyweights 36 carried in radial slots 37 in the cylindrical wall of the cup member causes the starter jaw to advance axiallyto the left as the spline nut rotates. Each flyweight is pivoted at one end on a pin 38 that is supported at its ends in the end walls of the slot. Projecting from the end wall of the flyweight is a center pin 39. Passing freely through a hole 41 in the opposite end of the flyweight is a pin 42 which pin is also supported at its ends in the end walls of the slot. The hole 41 is of a slightly larger diameter than the pin extending through it, and the wall of the hole limits the extent of angular movement of the flyweight. A leaf spring 43 inserted between the three pins tensions the flyweight angularly, and normally, to a position where one end of the weight is lowered slightly below the peripheral surface of the cup member and the opposite or pivot end 44 is raised slightly above this peripheral surface. The raised-ends of the flyweights bear against the inner wall of the starter jaw, and provide a frictional force against the latter which causes the starter jaw member to advance axially outward as the spline nut rotates. The starter jaw moves axially into engagement with the engine jaw. A flange 45 at the end of the starter jaw, limitable against the ends of the related splines, limits the extent to which the jaw may fully travel.

In general, in the engagement of starter and engine jaws, the ideal situation is where the teeth of the members engage or bottom fully with one another without the starter jaw exerting any axial force against the engine jaw mechanism, since this axial force can, at times, prove damaging to the engaging members. This manner of engagement requires very close tolerances in the positioning of the engaging members because of the limited depth of the engaging teeth, and particularly, where the engine jaw is a fixed part of the engine shaft.

The spring and shaft arrangement here of associating the engine jaw with the starter jaw avoids these difiiculties and the harmful effects mentioned. The engine jaw may by this arrangement be positioned axially relative to the starter jaw a distance, eitherequal to the extent of the travel of the starter jaw or to a distance slightly less. In either case, a fully bottomed meshing of the jaws will be effected without any harmful effects. In the second case where the tolerance is less than the traveling limit of the starter jaw, when the teeth engage, any axial force produced against the engine jaw by further travel of the starter jaw will cause the engine jaw to resiliently and harmlessly yield as the shaft is drawn slightly to the left against the tension of the coil spring 13. The engagement of the jaw members will be certain and fully bottomed.

It is to be noted that advancement of the starter jaw into engagement with the engine jaw can only occur when the starter speed is slightly greater than engine speed, thus avoiding ratcheting of the jaw teeth if the engine has some rotation when the starting cycle is initiated.

Subsequent to engagement of the jaw members, continued rotation of the starter mechanism drives the engine. The latter starts, and as its speed increases, it centrifugally forces the fiyweights to pivot outward. By this action the pivot ends 44 thereof will be drawn away free from the inner surface of the jaw member, and the opposite ends will, because of the limiting pin and hole, he held at the peripheral surface of the cup member also free of the inner wall of the starter jaw. This prevents the heavy flyweights from scoring the inner wall of the starter jaw as the engine rotates.

As the speed of the engine increases relative to the starter mechanism, the starter jaw in conventional manner disengages and travels back into the spline nut. A plurality of pins 46 are located in sockets in the lands forming the separating walls between the slots in cup member 33. These pins move radially outward in response to the rotation of the engine jaw and each bears lightly against the inner wall of the starter jaw. This action holds the starter jaw from creeping outwardly toward the rotating engine jaw, and thereby avoids the chattering of the jaws customarily associated with such creeping actions.

Upon disengagement of the jaw members, the power to the starter mechanism is cut olf in suitable manner. Bearing 35, whereby the engine jaw is associated with the shaft, enables the starter jaw to rotate about the shaft as the engine jaw is carried about by the associated engine.

A lip 48 about the flange of the engine jaw is abuttable against the end wall of the spline nut to thereby curb any creeping of the engine jaw toward the starter mechanism.

While an embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design and arrangement of the parts without departing from the spirit and scope of the invention, as the same will now be understood by those skilled in the art; and it is my intent, therefore, to claim the invention not only in the form shown and described, but also in all such formsand modifications thereof as may reasonably be construed to be within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. .In an engine starter assembly including a starter jaw and an oppositely positioned engine crank jaw, resilient means resiliently .holding .the engine jaw in axial spaced relation and alignment with the starter jaw so that the engine jaw can move axially during engagement, a support within the engine starter assembly for supporting the resilient means, anchor means for anchoring the'latter means to the support, and means for axially advancing the starter jaw into engagement with the engine aw.

2. In the combination of an engine crank jaw and a starter jaw for engaging the engine 'jaw and cranking the same, means for advancing the starter jaw into axial engagement with the engine jaw, means supporting the latter means, and resilient means resiliently anchoring the engine jaw to the support means and holding the same in spaced axial alignment with the starter jaw so that said engine jaw can move axially during engagement, said resilient means and said engine jaw being constructed so that said engine jaw can rotate relative to said support means.

3. In the combination ofa drive shaft, a fixed support rotatably supporting the drive shaft, a bell member geared for rotation to the drive shaft, 21 barrel member geared for rotation to the latter, a nut clutched for rotation with the barrel member, a starter jaw helically splined in the nut, and an engine jaw having teeth engageable by teeth in the starter jaw; a shaft rotatably retained at one end in a hollow interior of the starter jaw and spring retained at the-other end in a pocket of the bell member, the engine jaw being supported by the shaft in spaced axial-relation'to the starterjaw.

4. In engine starter mechanism of the character described, including a rotatable nut member, a starter jaw 'helically splined in the nut member for rotation therewith, an engine jaw disposed in axial spaced relation to the starter jaw, a member carried by the engine jaw and projecting axially into the interior of the starter jaw, and means contained in the member normally exerting a friction force upon the interior wall of the starter jaw, effective .to cause the latter to advance axially out of the out into engagement with the engine jaw upon rotation of the nut member.

5. In mechanism as in claim 4, wherein the friction exerting means comprises a plurality of weights pivoted in slots in the wall of the member and vtensioned by springs into frictional engagement with the interior wall of the starter jaw member.

6. In mechanism as in claim 4, wherein the friction exerting means comprises a plurality of arcuate llyweights, each pivotable at one end in a spline slot in the wall of the member, a pin fixed at its ends in opposed walls of the slots to limit the extent of such pivoting, a third pin .fixedin an end wall of each fiyweight and spring means tensioned between the pins of each weight and tensioning the weight in an angular direction wherein an end of the fiyweightfrictionally engages the interior wall of the sleeve, and the flyweights being centrifugally pivot- .able against the tension of the springs as the engine jaw is rotated by the starter jaw subsequent to engagement whereby the frictional force of the arcuate flyweights is .released from the member.

7. The combination in engine starter mechanism of a starter jaw, an engine jaw, means contained in the starter mechanism holding the engine jaw in axial spaced relation to the starter jaw, means for axially advancing the starter jaw into engagement with the engine jaw, means for rotating the engaged jaws together, means for retracting the starter jaw out of engagement from the engine jaw, a sleeve member carried by the engine jaw projecting axially into a hollow interior of the starter jaw in slight spaced relation to the inner wall of the latter, and pins radially slidable out of holes in the periphery of the sleeve member into engagement with the starter jaw wall to apply a friction force thereto in response to centrifugal forces created by the rotating engine jaw, the

friction force being efiective to restrain the starter jaw from creeping out to re-engage the engine jaw subsequent to disengagement of the jaws.

References Cited in the file of this patent UNITED STATES PATENTS 

